HARQ LLR buffer and reordering buffer management

ABSTRACT

Certain aspects of the present disclosure relate to methods and apparatus for management of hybrid automatic repeat request (HARQ) log likelihood ratio (LLR) and reordering buffers in wireless communication systems. According to certain aspects, a method for reducing buffer overhead that may be performed by a wireless node is provided. The method generally includes receiving one or more packets of at least one of an initial transmission or a retransmission; forming one or more log likelihood ratios (LLRs) based on the one or more packets; compressing the one or more LLRs by quantizing the one or more LLRs; and buffering the one or more compressed LLRs.

CROSS-REFERENCE TO RELATED APPLICATION & PRIORITY CLAIM

This application claims benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 62/279,994, filed Jan. 18, 2016, which isherein incorporated by reference in its entirety for all applicablepurposes.

BACKGROUND Field of the Disclosure

The present disclosure relates generally to wireless communication, andmore particularly, to methods and apparatus for management of hybridautomatic repeat request (HARQ) log likelihood ratio (LLR) buffers andreordering buffers in wireless communication systems.

Description of Related Art

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includecode division multiple access (CDMA) systems, time division multipleaccess (TDMA) systems, frequency division multiple access (FDMA)systems, orthogonal frequency division multiple access (OFDMA) systems,single-carrier frequency divisional multiple access (SC-FDMA) systems,and time division synchronous code division multiple access (TD-SCDMA)systems.

In some examples, a wireless multiple-access communication system mayinclude a number of base stations (BSs), each simultaneously supportingcommunication for multiple communication devices, otherwise known asuser equipment (UEs). In long term evolution (LTE) or LTE Advanced(LTE-A) networks, a set of one or more BSs may define anenhanced/evolved Node B (eNB). In other examples (e.g., in a nextgeneration, new radio (NR), or 5G network), a wireless multiple-accesscommunication system may include a number of distributed units (DUs)(e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smartradio heads (SRHs), transmission reception points (TRPs), etc.) incommunication with a number of central units (CUs) (e.g., central nodes(CNs), access node controllers (ANCs), etc.), where a set of one or moredistributed units, in communication with a central unit, may define anaccess node (e.g., a NR BS, a NR NB, a network node, a 5G NB, a gNB, anaccess point (AP), etc.). A BS or DU may communicate with a set of UEson downlink channels (e.g., for transmissions from a base station or toa UE) and uplink channels (e.g., for transmissions from a UE to a BS orDU).

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is Long Term Evolution (LTE).LTE/LTE-Advanced is a set of enhancements to the Universal MobileTelecommunications System (UMTS) mobile standard promulgated by ThirdGeneration Partnership Project (3GPP). An example of an emergingtelecommunication standard is NR, for example, 5G radio access. NR is aset of enhancements to the LTE mobile standard promulgated by 3GPP. Itis designed to better support mobile broadband Internet access byimproving spectral efficiency, lowering costs, improving services,making use of new spectrum, and better integrating with other openstandards using OFDMA with a cyclic prefix (CP) on the downlink (DL) andon the uplink (UL) as well as support beamforming, multiple-inputmultiple-output (MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a need for further improvements in LTE and NRtechnology. Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

The present disclosure relates generally to wireless communication, andmore particularly, to methods and apparatus for management of hybridautomatic repeat request (HARQ) log likelihood ratio (LLR) buffers andreordering buffers in wireless communication systems.

Certain aspects of the present disclosure provide a method to reducebuffer overhead that can be performed by a wireless node, such as a userequipment (UE) or a base station (BS). The method generally includesreceiving one or more packets of at least one of an initial transmissionor a retransmission; forming one or more LLRs based on the one or morepackets; compressing the one or more LLRs by quantizing the one or moreLLRs; and buffering the one or more compressed LLRs.

Certain aspects of the present disclosure provide a method to reducebuffer overhead that can be performed by a wireless node, such as a UEor BS. The method generally includes receiving an initial transmissionor a retransmission comprising one or more transmission blocks on atleast one of multiple component carriers (CCs) or multiple HARQinterlaces; attempting to decode the one or more transmission blocks;determining whether the one or more transmission blocks weresuccessfully decoded; storing soft LLRs associated with transmissionblocks that failed to successfully decode in a shared buffer; andstoring transmission blocks that were successfully decoded out-of-orderin the shared buffer.

Certain aspects of the present disclosure provide a method for wirelesscommunication that can be performed by a wireless node, such as a UE orBS. The method generally includes sending a retransmission on at leastone of multiple CCs or multiple HARQ interlaces; and sending one or moreparity packets associated with at least a portion of the retransmission.

Certain aspects of the present disclosure provide an apparatus havingreduced buffer overhead. The apparatus generally includes means forreceiving one or more packets of at least one of an initial transmissionor a retransmission; means for forming one or more LLRs based on the oneor more packets; means for compressing the one or more LLRs byquantizing the one or more LLRs; and means for buffering the one or morecompressed LLRs.

Certain aspects of the present disclosure provide an apparatus havingreduced buffer overhead. The apparatus generally includes means forreceiving an initial transmission or a retransmission comprising one ormore transmission blocks on at least one of multiple CCs or multipleHARQ interlaces; means for attempting to decode the one or moretransmission blocks; means for determining whether the one or moretransmission blocks were successfully decoded; means for storing softLLRs associated with transmission blocks that failed to successfullydecode in a shared buffer; and means for storing transmission blocksthat were successfully decoded out-of-order in the shared buffer.

Certain aspects of the present disclosure provide an apparatus forwireless communication. The apparatus generally includes means forsending a retransmission on at least one of multiple CCs or multipleHARQ interlaces; and means for sending one or more parity packetsassociated with at least a portion of the retransmission.

Certain aspects of the present disclosure provide an apparatus havingreduced buffer overhead such as a wireless node (e.g., a UE or BS). Theapparatus generally includes at least one processor configured to:receive one or more packets of at least one of an initial transmissionor a retransmission; form one or more LLRs based on the one or morepackets; compress the one or more LLRs by quantizing the one or moreLLRs; and a memory coupled with the at least one processor; and bufferthe one or more compressed LLRs.

Certain aspects of the present disclosure provide an apparatus havingreduced buffer overhead such as a wireless node (e.g., a UE or BS). Theapparatus generally includes at least one processor configured to:receive an initial transmission or a retransmission comprising one ormore transmission blocks on at least one of multiple CCs or multipleHARQ interlaces; attempt to decode the one or more transmission blocks;determine whether the one or more transmission blocks were successfullydecoded; store soft LLRs associated with transmission blocks that failedto successfully decode in a shared buffer; and store transmission blocksthat were successfully decoded out-of-order in the shared buffer; and amemory coupled with the at least one processor.

Certain aspects of the present disclosure provide an apparatus forwireless communications such as a wireless node (e.g., a UE or BS). Theapparatus generally includes at least one processor configured to: senda retransmission on at least one of multiple CCs or multiple HARQinterlaces; and send one or more parity packets associated with at leasta portion of the retransmission; and a memory coupled with the at leastone processor.

Certain aspects of the present disclosure provide a computer readablemedium having computer executable code stored thereon for reducingbuffer overhead. The computer executable code generally includes codefor receiving one or more packets of at least one of an initialtransmission or a retransmission; code for forming one or more LLRsbased on the one or more packets; code for compressing the one or moreLLRs by quantizing the one or more LLRs; and code for buffering the oneor more compressed LLRs.

Certain aspects of the present disclosure provide a computer readablemedium having computer executable code stored thereon for reducingbuffer overhead. The computer executable code generally includes codefor receiving an initial transmission or a retransmission comprising oneor more transmission blocks on at least one of multiple CCs or multipleHARQ interlaces; code for attempting to decode the one or moretransmission blocks; code for determining whether the one or moretransmission blocks were successfully decoded; code for storing softLLRs associated with transmission blocks that failed to successfullydecode in a shared buffer; and code for storing transmission blocks thatwere successfully decoded out-of-order in the shared buffer.

Certain aspects of the present disclosure provide a computer readablemedium having computer executable code stored thereon for wirelesscommunications. The computer executable code generally includes code forsending a retransmission on at least one of multiple CCs or multipleHARQ interlaces; and code for sending one or more parity packetsassociated with at least a portion of the retransmission.

Other aspects, features, and embodiments of the present invention willbecome apparent to those of ordinary skill in the art, upon reviewingthe following description of specific, exemplary embodiments of thepresent invention in conjunction with the accompanying figures. Whilefeatures of the present invention may be discussed relative to certainembodiments and figures below, all embodiments of the present inventioncan include one or more of the advantageous features discussed herein.In other words, while one or more embodiments may be discussed as havingcertain advantageous features, one or more of such features may also beused in accordance with the various embodiments of the inventiondiscussed herein. In similar fashion, while exemplary embodiments may bediscussed below as device, system, or method embodiments it should beunderstood that such exemplary embodiments can be implemented in variousdevices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. The appended drawingsillustrate only certain typical aspects of this disclosure, however, andare therefore not to be considered limiting of its scope, for thedescription may admit to other equally effective aspects.

FIG. 1 is a diagram illustrating an example of a network architecture.

FIG. 2 is a diagram illustrating an example of an access network.

FIG. 3 is a diagram illustrating an example of a DL frame structure inan access network.

FIG. 4 is a diagram illustrating an example of an UL frame structure inan access network.

FIG. 5 is a diagram illustrating an example of a radio protocolarchitecture for the user and control plane.

FIG. 6 is a diagram illustrating an example of a base station (BS) anduser equipment (UE) in an access network, in accordance with certainaspects of the disclosure.

FIG. 7 illustrates an example logical architecture of a distributedradio access network (RAN), in accordance with certain aspects of thepresent disclosure.

FIG. 8 illustrates an example physical architecture of a distributedRAN, in accordance with certain aspects of the present disclosure.

FIG. 9 is a diagram illustrating an example of a downlink (DL)-centricsubframe, in accordance with certain aspects of the present disclosure.

FIG. 10 is a diagram illustrating an example of an uplink (UL)-centricsubframe, in accordance with certain aspects of the present disclosure.

FIG. 11 is a representation of an example hybrid automatic repeatrequest (HARQ) buffer with interleaved bits, systematic bits, andredundant bits, in accordance with certain aspects of the presentdisclosure.

FIG. 12 is a flow diagram illustrating example operations forlog-likelihood ratio (LLR) buffer management by a receiver, inaccordance with certain aspects of the present disclosure.

FIG. 13 is a block diagram illustrating example 3-level LLRs compressedto binary format, in accordance with certain aspects of the presentdisclosure.

FIG. 14 is a graph illustrating example performance of HARQ incrementalredundancy (IR) combining, in accordance with certain aspects of thepresent disclosure.

FIG. 15 is a flow diagram illustrating example operations for sharedHARQ LLR buffer and reordering buffer management by a receiver, inaccordance with certain aspects of the present disclosure.

FIG. 16 illustrates example decoding results for a single HARQ interlaceon a single component carrier (CC), in accordance with certain aspectsof the present disclosure.

FIG. 17 illustrates example decoding results for a single HARQ interlaceon multiple CCs, in accordance with certain aspects of the presentdisclosure.

FIG. 18 illustrates example decoding results for a single HARQ interlacewith parity packets on multiple CCs, in accordance with certain aspectsof the present disclosure.

FIG. 19 is a flow diagram illustrating example operations for wirelesscommunications by a transmitter, in accordance with certain aspects ofthe present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processingsystems, and computer readable mediums for hybrid automatic repeatrequest (HARQ) log-likelihood ratio (LLR) buffer and reordering buffermanagement.

Aspects of the present disclosure may be used for new radio (NR) (newradio access technology or 5G technology). NR may support variouswireless communication services, such as Enhanced mobile broadband(eMBB) targeting wide bandwidth (e.g. 80 MHz beyond), millimeter wave(mmW) targeting high carrier frequency (e.g. 60 GHz), massive machinetype communications (mMTC) targeting non-backward compatible MTCtechniques, and/or mission critical targeting ultra-reliable low latencycommunications (URLLC). These services may include latency andreliability requirements. These services may also have differenttransmission time intervals (TTI) to meet respective quality of service(QoS) requirements. In addition, these services may co-exist in the samesubframe.

Scaling of conventional hybrid automatic repeat request (HARQ) buffermanagement of certain systems, such as long term evolution (LTE) HARQmay lead to high overhead for other systems that support higherthroughput, for example, NR systems such as 5G systems. Aspects of thepresent disclosure provide techniques for HARQ LLR buffer and ARQreordering buffer management. For example, these techniques include lowbitwidth LLR quantization and/or a joint LLR and reordering buffer.

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim. The word “exemplary”is used herein to mean “serving as an example, instance, orillustration.” Any aspect described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otheraspects.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

The techniques described herein may be used for various wirelesscommunication networks such as LTE, Code Division Multiple Access (CDMA)networks, Time Division Multiple Access (TDMA) networks, FrequencyDivision Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms“networks” and “systems” are often used interchangeably. A CDMA networkmay implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), CDMA2000, etc. UTRA includes Wideband-CDMA (W-CDMA) andLow Chip Rate (LCR). CDMA2000 covers IS-2000, IS-95, and IS-856standards. A TDMA network may implement a radio technology such asGlobal System for Mobile Communications (GSM). An OFDMA network mayimplement a radio technology such as NR (e.g., 5G radio access), EvolvedUTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20,Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part of Universal MobileTelecommunication System (UMTS). LTE is a release of UMTS that usesE-UTRA. UTRA, E-UTRA, GSM, UMTS, and LTE are described in documents froman organization named “3rd Generation Partnership Project” (3GPP).CDMA2000 is described in documents from an organization named “3rdGeneration Partnership Project 2” (3GPP2). NR is an emerging wirelesscommunications technology under development in conjunction with the 5GTechnology Forum (5GTF). These communications networks are merely listedas examples of networks in which the techniques described in thisdisclosure may be applied; however, this disclosure is not limited tothe above-described communications network. For clarity, while aspectsmay be described herein using terminology commonly associated with 3Gand/or 4G wireless technologies, aspects of the present disclosure canbe applied in other generation-based communication systems, such as NRtechnologies, including 5G and later.

Example Wireless Communications Systems

FIG. 1 is a diagram illustrating a network architecture 100 in whichaspects of the present disclosure may be practiced. For example, thewireless network may be a new radio (NR) or 5G network. BSs 106 and/orUEs 120 may be configured to perform the operations 1200, 1500, and 1900and methods described herein for hybrid automatic repeat request (HARQ)LLR buffer and reordering buffer management.

For example, a receiver, such as a wireless node (e.g., a UE 102 or BS106) may receive packets in a transmission or a retransmission from atransmitter (e.g., UE 102 or BS 106). The receiver may form one or morelog likelihood ratios (LLRs) based on the one or more packets receivedfrom the transmitter and compress the one or more LLRs by quantizing theLLRs and mapping combinations of groups of quantized LLRs to bits. Inaddition, or alternatively, the receiver may store LLRs of failedtransmission blocks in a shared buffer and may also store successfullydecoded transmission blocks in the shared buffer.

The network architecture 100 may be referred to as an Evolved PacketSystem (EPS) 100 (e.g., long term evolution (LTE)). EPS 100 may includeone or more user equipment (UE) 102, an Evolved UMTS Terrestrial RadioAccess Network (E-UTRAN) 104, an Evolved Packet Core (EPC) 110, a HomeSubscriber Server (HSS) 120, and an Operator's IP Services 122. EPS 100can interconnect with other access networks, but for simplicity thoseentities/interfaces are not shown. Exemplary other access networks mayinclude an IP Multimedia Subsystem (IMS) packet data network (PDN),Internet PDN, Administrative PDN (e.g., Provisioning PDN),carrier-specific PDN, operator-specific PDN, and/or Global PositioningSystem (GPS) PDN. As shown, the EPS provides packet-switched (PS)services, however, as those skilled in the art will readily appreciate,the various concepts presented throughout this disclosure may beextended to networks providing circuit-switched (CS) services.

A UE 102 may also be referred to as a mobile station, a terminal, anaccess terminal, a subscriber unit, a station, a Customer PremisesEquipment (CPE), a cellular phone, a smart phone, a personal digitalassistant (PDA), a wireless modem, a wireless communication device, ahandheld device, a laptop computer, a cordless phone, a wireless localloop (WLL) station, a tablet, a camera, a gaming device, a netbook, asmartbook, an ultrabook, a medical device or medical equipment, abiometric sensor/device, a wearable device such as a smart watch, smartclothing, smart glasses, a smart wrist band, smart jewelry (e.g., asmart ring, a smart bracelet, etc.), an entertainment device (e.g., amusic device, a video device, a satellite radio, etc.), a vehicularcomponent or sensor, a smart meter/sensor, industrial manufacturingequipment, a global positioning system device, or any other suitabledevice that is configured to communicate via a wireless or wired medium.Some UEs may be considered evolved or machine-type communication (MTC)devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, forexample, robots, drones, remote devices, sensors, meters, monitors,location tags, etc., that may communicate with a BS, another device(e.g., remote device), or some other entity. A wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as Internet or a cellular network) via a wired orwireless communication link. Some UEs may be consideredInternet-of-Things (IoT) devices.

The E-UTRAN includes the base station (BS) 106 and other BSs 108. The BS106 provides user and control plane protocol terminations toward the UE102. The BS 106 may be connected to the other BSs 108 via an X2interface (e.g., backhaul). The BS 106 may also be referred to as a basetransceiver station, a radio base station, a radio transceiver, atransceiver function, a basic service set (BSS), an extended service set(ESS), an access point, an enhanced/evolved Node B (eNB), or some othersuitable terminology. The BS 106 may provide an access point to the EPC110 for a UE 102.

A BS may be a station that communicates with UEs. Each BS 110 mayprovide communication coverage for a particular geographic area. In3GPP, the term “cell” can refer to a coverage area of a Node B and/or aNode B subsystem serving this coverage area, depending on the context inwhich the term is used. In NR systems, the term “cell” and gNB, Node B,5G NB, AP, NR BS, NR BS, or TRP may be interchangeable. In someexamples, a cell may not necessarily be stationary, and the geographicarea of the cell may move according to the location of a mobile basestation. In some examples, the base stations may be interconnected toone another and/or to one or more other base stations or network nodes(not shown) in the wireless network 100 through various types ofbackhaul interfaces such as a direct physical connection, a virtualnetwork, or the like using any suitable transport network.

The BS 106 is connected by an S1 interface to the EPC 110. The EPC 110includes a Mobility Management Entity (MME) 112, other MMEs 114, aServing Gateway 116, and a Packet Data Network (PDN) Gateway 118. TheMME 112 is the control node that processes the signaling between the UE102 and the EPC 110. Generally, the MME 112 provides bearer andconnection management. All user IP packets are transferred through theServing Gateway 116, which itself is connected to the PDN Gateway 118.The PDN Gateway 118 provides UE IP address allocation as well as otherfunctions. The PDN Gateway 118 is connected to the Operator's IPServices 122. The Operator's IP Services 122 may include, for example,the Internet, the Intranet, an IP Multimedia Subsystem (IMS), and a PS(packet-switched) Streaming Service (PSS). In this manner, the UE 102may be coupled to the PDN through the network architecture 100.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a frequencychannel, etc. Each frequency may support a single RAT in a givengeographic area in order to avoid interference between wireless networksof different RATs. In some cases, NR or 5G RAT networks may be deployed.While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR or 5G.

FIG. 2 is a diagram illustrating an example of an access network 200 ina network architecture in which aspects of the present disclosure may bepracticed. For example, BSs 204 and UEs 206 may be configured toimplement techniques for HARQ LLR buffer and reordering buffermanagement, in accordance with certain aspects of the presentdisclosure.

In this example, access network 200 is divided into a number of cellularregions (cells) 202. One or more lower power class BSs 208 may havecellular regions 210 that overlap with one or more of the cells 202. Alower power class BS 208 may be referred to as a remote radio head(RRH). The lower power class BS 208 may be a femto cell (e.g., home BS),pico cell, or micro cell. The macro BSs 204 are each assigned to arespective cell 202 and are configured to provide an access point to theEPC 110 for all the UEs 206 in the cells 202. There is no centralizedcontroller in this example of access network 200, but a centralizedcontroller may be used in alternative configurations. BSs 204 areresponsible for all radio related functions including radio bearercontrol, admission control, mobility control, scheduling, security, andconnectivity to the serving gateway 116. Access network 200 may alsoinclude one or more relays (not shown). According to aspects, a UE mayserve as a relay.

In NR systems, the term “cell” and gNB, Node B, 5G NB, or TRP may beinterchangeable. In some examples, a cell may not necessarily bestationary, and the geographic area of the cell may move according tothe location of a mobile base station. In some examples, the basestations may be interconnected to one another and/or to one or moreother base stations or network nodes (not shown) in the access network100 through various types of backhaul interfaces such as a directphysical connection, a virtual network, or the like using any suitabletransport network.

The modulation and multiple access scheme employed by access network 200may vary depending on the particular telecommunications standard beingdeployed. As those skilled in the art will readily appreciate from thedetailed description to follow, the various concepts presented hereinare well suited for certain applications, such as LTE, NR, and 5G.However, these concepts may be readily extended to othertelecommunication standards employing other modulation and multipleaccess techniques. The actual wireless communication standard and themultiple access technology employed will depend on the specificapplication and the overall design constraints imposed on the system.

BSs 204 may have multiple antennas supporting MIMO technology. The useof MIMO technology enables the BSs 204 to exploit the spatial domain tosupport spatial multiplexing, beamforming, and transmit diversity.Spatial multiplexing may be used to transmit different streams of datasimultaneously on the same frequency. The data streams may betransmitted to a single UE 206 to increase the data rate or to multipleUEs 206 to increase the overall system capacity. This is achieved byspatially precoding each data stream (e.g., applying a scaling of anamplitude and a phase) and then transmitting each spatially precodedstream through multiple transmit antennas on the DL. The spatiallyprecoded data streams arrive at the UE(s) 206 with different spatialsignatures, which enables each of the UE(s) 206 to recover the one ormore data streams destined for that UE 206. On the UL, each UE 206transmits a spatially precoded data stream, which enables BS 204 toidentify the source of each spatially precoded data stream.

Spatial multiplexing is generally used when channel conditions are good.When channel conditions are less favorable, beamforming may be used tofocus the transmission energy in one or more directions. This may beachieved by spatially precoding the data for transmission throughmultiple antennas. To achieve good coverage at the edges of the cell, asingle stream beamforming transmission may be used in combination withtransmit diversity.

In the detailed description that follows, various aspects of an accessnetwork will be described with reference to a MIMO system supportingOFDM on the DL. OFDM is a spread-spectrum technique that modulates dataover a number of subcarriers within an OFDM symbol. The subcarriers arespaced apart at precise frequencies. The spacing provides“orthogonality” that enables a receiver to recover the data from thesubcarriers. In the time domain, a guard interval (e.g., cyclic prefix)may be added to each OFDM symbol to combat inter-OFDM-symbolinterference. The UL may use SC-FDMA in the form of a DFT-spread OFDMsignal to compensate for high peak-to-average power ratio (PAPR).

In some examples, access to the air interface may be scheduled. Ascheduling entity (e.g., a BS) can allocate resources for communicationamong some or all devices and equipment within its service area or cell.Within the present disclosure, as discussed further below, thescheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity.

BSs are not the only entities that may function as a scheduling entity.That is, in some examples, a UE may function as a scheduling entity,scheduling resources for one or more subordinate entities (e.g., one ormore other UEs). In this example, the UE is functioning as a schedulingentity, and other UEs utilize resources scheduled by the UE for wirelesscommunication. A UE may function as a scheduling entity in apeer-to-peer (P2P) network, and/or in a mesh network. In a mesh networkexample, UEs may optionally communicate directly with one another inaddition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access totime-frequency resources and having a cellular configuration, a P2Pconfiguration, and a mesh configuration, a scheduling entity and one ormore subordinate entities may communicate utilizing the scheduledresources.

FIG. 3 is a diagram 300 illustrating an example of a DL frame structurein an access network (e.g., LTE). A frame (10 ms) may be divided into 10equally sized subframes with indices of 0 through 9. Each sub-frame mayinclude two consecutive time slots. A resource grid may be used torepresent two time slots, each time slot including a resource block(RB). The resource grid is divided into multiple resource elements. Incertain systems (e.g., LTE), a RB contains 12 consecutive subcarriers inthe frequency domain and, for a normal cyclic prefix in each OFDMsymbol, 7 consecutive OFDM symbols in the time domain, or 84 resourceelements (REs). For an extended cyclic prefix, a RB contains 6consecutive OFDM symbols in the time domain and has 72 REs. Some of theREs, as indicated as R 302, R 304, include DL reference signals (DL-RS).The DL-RS include Cell-specific RS (CRS) (also sometimes called commonRS) 302 and UE-specific RS (UE-RS) 304. UE-RS 304 are transmitted onlyon the RBs upon which the corresponding physical DL shared channel(PDSCH) is mapped. The number of bits carried by each RE depends on themodulation scheme. Thus, the more RBs that a UE receives and the higherthe modulation scheme, the higher the data rate for the UE.

In certain systems (e.g., LTE), a BS may send a primary synchronizationsignal (PSS) and a secondary synchronization signal (SSS) for each cellin the BS. The PSS and SSS may be sent in symbol periods 6 and 5,respectively, in each of subframes 0 and 5 of each radio frame with thenormal cyclic prefix (CP). The synchronization signals may be used byUEs for cell detection and acquisition. The BS may send a PhysicalBroadcast Channel (PBCH) in symbol periods 0 to 3 in slot 1 of subframe0. The PBCH may carry certain system information.

The BS may send a Physical Control Format Indicator Channel (PCFICH) inthe first symbol period of each subframe. The PCFICH may convey thenumber of symbol periods (M) used for control channels, where M may beequal to 1, 2 or 3 and may change from subframe to subframe. M may alsobe equal to 4 for a small system bandwidth, e.g., with less than 10 RBs.The BS may send a Physical HARQ Indicator Channel (PHICH) and a PhysicalDownlink Control Channel (PDCCH) in the first M symbol periods of eachsubframe. The PHICH may carry information to support hybrid automaticrepeat request (HARQ). The PDCCH may carry information on resourceallocation for UEs and control information for downlink channels. The BSmay send a Physical Downlink Shared Channel (PDSCH) in the remainingsymbol periods of each subframe. The PDSCH may carry data for UEsscheduled for data transmission on the downlink.

The BS may send the PSS, SSS, and PBCH in the center 1.08 MHz of thesystem bandwidth used by the BS. The BS may send the PCFICH and PHICHacross the entire system bandwidth in each symbol period in which thesechannels are sent. The BS may send the PDCCH to groups of UEs in certainportions of the system bandwidth. The BS may send the PDSCH to specificUEs in specific portions of the system bandwidth. The BS may send thePSS, SSS, PBCH, PCFICH, and PHICH in a broadcast manner to all UEs, maysend the PDCCH in a unicast manner to specific UEs, and may also sendthe PDSCH in a unicast manner to specific UEs.

A number of REs may be available in each symbol period. Each RE maycover one subcarrier in one symbol period and may be used to send onemodulation symbol, which may be a real or complex value. REs not usedfor a reference signal in each symbol period may be arranged intoresource element groups (REGs). Each REG may include four REs in onesymbol period. The PCFICH may occupy four REGs, which may be spacedapproximately equally across frequency, in symbol period 0. The PHICHmay occupy three REGs, which may be spread across frequency, in one ormore configurable symbol periods. For example, the three REGs for thePHICH may all belong in symbol period 0 or may be spread in symbolperiods 0, 1, and 2. The PDCCH may occupy 9, 18, 36, or 72 REGs, whichmay be selected from the available REGs, in the first M symbol periods,for example. Only certain combinations of REGs may be allowed for thePDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. TheUE may search different combinations of REGs for the PDCCH. The numberof combinations to search is typically less than the number of allowedcombinations for the PDCCH. A BS may send the PDCCH to the UE in any ofthe combinations that the UE will search.

FIG. 4 is a diagram 400 illustrating an example of an UL frame structurein a wireless communications system (e.g., LTE). The available RBs forthe UL may be partitioned into a data section and a control section. Thecontrol section may be formed at the two edges of the system bandwidthand may have a configurable size. The RBs in the control section may beassigned to UEs for transmission of control information. The datasection may include all RBs not included in the control section. The ULframe structure results in the data section including contiguoussubcarriers, which may allow a single UE to be assigned all of thecontiguous subcarriers in the data section.

A UE may be assigned RBs 410 a, 410 b in the control section to transmitcontrol information to a BS. The UE may also be assigned RBs 420 a, 420b in the data section to transmit data to the BS. The UE may transmitcontrol information in a physical UL control channel (PUCCH) on theassigned RBs in the control section. The UE may transmit only data orboth data and control information in a physical UL shared channel(PUSCH) on the assigned RBs in the data section. A UL transmission mayspan both slots of a subframe and may hop across frequency.

A set of RBs may be used to perform initial system access and achieve ULsynchronization in a physical random access channel (PRACH) 430. PRACH430 carries a random sequence and cannot carry any UL data/signaling.Each random access preamble occupies a bandwidth corresponding to sixconsecutive RBs. The starting frequency is specified by the network.That is, the transmission of the random access preamble is restricted tocertain time and frequency resources. There is no frequency hopping forthe PRACH. The PRACH attempt is carried in a single subframe (1 ms) orin a sequence of few contiguous subframes and a UE can make only asingle PRACH attempt per frame (10 ms).

In other systems (e.g., such NR or 5G systems), a BS may transmit theseor other signals in these locations or in different locations of thesubframe. As will described in more detail below with respect to FIGS. 9and 10, in other systems (e.g., NR or 5G systems), different uplinkand/or downlink frame structures may be used.

FIG. 5 is a diagram 500 illustrating an example of a radio protocolarchitecture for the user and control planes in an example wirelesscommunications systems (e.g., LTE). The radio protocol architecture forthe UE and the BS is shown with three layers: Layer 1, Layer 2, andLayer 3. Layer 1 (L1 layer) is the lowest layer and implements variousphysical layer signal processing functions. The L1 layer will bereferred to herein as the physical layer 506. Layer 2 (L2 layer) 508 isabove the physical layer 506 and is responsible for the link between theUE and BS over the physical layer 506.

In the user plane, the L2 layer 508 includes a media access control(MAC) sublayer 510, a radio link control (RLC) sublayer 512, and apacket data convergence protocol (PDCP) 514 sublayer, which areterminated at the BS on the network side. Although not shown, the UE mayhave several upper layers above the L2 layer 508 including a networklayer (e.g., IP layer) that is terminated at the PDN gateway 118 on thenetwork side, and an application layer that is terminated at the otherend of the connection (e.g., far end UE, server, etc.).

The PDCP sublayer 514 provides multiplexing between different radiobearers and logical channels. The PDCP sublayer 514 also provides headercompression for upper layer data packets to reduce radio transmissionoverhead, security by ciphering the data packets, and handover supportfor UEs between BSs. The RLC sublayer 512 provides segmentation andreassembly of upper layer data packets, retransmission of lost datapackets, and reordering of data packets to compensate for out-of-orderreception due to HARQ. The MAC sublayer 510 provides multiplexingbetween logical and transport channels. The MAC sublayer 510 is alsoresponsible for allocating the various radio resources (e.g., RBs) inone cell among the UEs. The MAC sublayer 510 is also responsible forHARQ operations.

In the control plane, the radio protocol architecture for the UE and BSis substantially the same for the physical layer 506 and the L2 layer508 with the exception that there is no header compression function forthe control plane. The control plane also includes a radio resourcecontrol (RRC) sublayer 516 in Layer 3 (L3 layer). The RRC sublayer 516is responsible for obtaining radio resources (i.e., radio bearers) andfor configuring the lower layers using RRC signaling between the BS andthe UE.

FIG. 6 is a block diagram of a BS 610 in communication with a UE 650 inan access network, in which aspects of the present disclosure may bepracticed.

In the DL, upper layer packets from the core network are provided to acontroller/processor 675. The controller/processor 675 implements thefunctionality of the L2 layer. In the DL, the controller/processor 675provides header compression, ciphering, packet segmentation andreordering, multiplexing between logical and transport channels, andradio resource allocations to the UE 650 based on various prioritymetrics. The controller/processor 675 is also responsible for HARQoperations, retransmission of lost packets, and signaling to the UE 650.

The TX processor 616 implements various signal processing functions forthe L1 layer (i.e., physical layer). The signal processing functionsincludes coding and interleaving to facilitate forward error correction(FEC) at the UE 650 and mapping to signal constellations based onvarious modulation schemes (e.g., binary phase-shift keying (BPSK),quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK),M-quadrature amplitude modulation (M-QAM)). The coded and modulatedsymbols are then split into parallel streams. Each stream is then mappedto an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot)in the time and/or frequency domain, and then combined together using anInverse Fast Fourier Transform (IFFT) to produce a physical channelcarrying a time domain OFDM symbol stream. The OFDM stream is spatiallyprecoded to produce multiple spatial streams. Channel estimates from achannel estimator 674 may be used to determine the coding and modulationscheme, as well as for spatial processing. The channel estimate may bederived from a reference signal and/or channel condition feedbacktransmitted by the UE 650. Each spatial stream is then provided to adifferent antenna 620 via a separate transmitter 618TX. Each transmitter618TX modulates an RF carrier with a respective spatial stream fortransmission.

At the UE 650, each receiver 654RX receives a signal through itsrespective antenna 652. Each receiver 654RX recovers informationmodulated onto an RF carrier and provides the information to thereceiver (RX) processor 656. The RX processor 656 implements varioussignal processing functions of the L1 layer. The RX processor 656performs spatial processing on the information to recover any spatialstreams destined for the UE 650. If multiple spatial streams aredestined for the UE 650, they may be combined by the RX processor 656into a single OFDM symbol stream. The RX processor 656 then converts theOFDM symbol stream from the time-domain to the frequency domain using aFast Fourier Transform (FFT). The frequency domain signal comprises aseparate OFDM symbol stream for each subcarrier of the OFDM signal. Thesymbols on each subcarrier, and the reference signal, is recovered anddemodulated by determining the most likely signal constellation pointstransmitted by the BS 610. These soft decisions may be based on channelestimates computed by the channel estimator 658. The soft decisions arethen decoded and deinterleaved to recover the data and control signalsthat were originally transmitted by the BS 610 on the physical channel.The data and control signals are then provided to thecontroller/processor 659.

The controller/processor 659 implements the L2 layer. Thecontroller/processor can be associated with a memory 660 that storesprogram codes and data. The memory 660 may be referred to as acomputer-readable medium. In the UL, the control/processor 659 providesdemultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the core network. The upper layerpackets are then provided to a data sink 662, which represents all theprotocol layers above the L2 layer. Various control signals may also beprovided to the data sink 662 for L3 processing. Thecontroller/processor 659 is also responsible for error detection usingan acknowledgement (ACK) and/or negative acknowledgement (NACK) protocolto support HARQ operations.

In the UL, a data source 667 is used to provide upper layer packets tothe controller/processor 659. The data source 667 represents allprotocol layers above the L2 layer. Similar to the functionalitydescribed in connection with the DL transmission by BS 610, thecontroller/processor 659 implements the L2 layer for the user plane andthe control plane by providing header compression, ciphering, packetsegmentation and reordering, and multiplexing between logical andtransport channels based on radio resource allocations by BS 610.Controller/processor 659 is also responsible for HARQ operations,retransmission of lost packets, and signaling to the BS 610.

Channel estimates derived by a channel estimator 658 from a referencesignal or feedback transmitted by BS 610 may be used by the TX processor668 to select the appropriate coding and modulation schemes, and tofacilitate spatial processing. The spatial streams generated by the TXprocessor 668 are provided to different antenna 652 via separatetransmitters 654TX. Each transmitter 654TX modulates an RF carrier witha respective spatial stream for transmission.

The UL transmission is processed at BS 610 in a manner similar to thatdescribed in connection with the receiver function at the UE 650. Eachreceiver 618RX receives a signal through its respective antenna 620.Each receiver 618RX recovers information modulated onto an RF carrierand provides the information to a RX processor 670. The RX processor 670may implement the L1 layer.

The controller/processor 675 implements the L2 layer.Controller/processor 675 can be associated with a memory 676 that storesprogram codes and data. The memory 676 may be referred to as acomputer-readable medium. In the UL, control/processor 675 providesdemultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from UE 650. Upper layer packets fromcontroller/processor 675 may be provided to the core network.Controller/processor 675 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations. Thecontrollers/processors 675, 659 may direct the operations at the BS 610and UE 650, respectively.

Controller/processor 675 and/or other processors and modules at BS 610and controller/processor 659 and/or other processors and modules at UE650 may perform or direct operations, for example, operations 1200 inFIG. 12, operations 1500 in FIG. 15, operations 1900 in FIG. 19, and/orother processes for the techniques described herein for HARQ LLR bufferand reordering buffer management. The memories 660 and 676 may storedata and program codes for the UE 650 and BS 610 respectively,accessible and executable by one or more other components of the UE 650and the BS 610.

Example NR/5G RAN Architecture

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR or 5Gtechnologies.

New radio (NR) may refer to radios configured to operate according to anew air interface (e.g., other than Orthogonal Frequency DivisionalMultiple Access (OFDMA)-based air interfaces) or fixed transport layer(e.g., other than Internet Protocol (IP)). NR may utilize OFDM with acyclic prefix (CP) on the uplink and downlink and may include supportfor half-duplex operation using time division duplexing (TDD). NR mayinclude Enhanced Mobile Broadband (eMBB) service targeting widebandwidth (e.g. 80 MHz beyond), millimeter wave (mmW) targeting highcarrier frequency (e.g. 60 GHz), massive MTC (mMTC) targetingnon-backward compatible MTC techniques, and/or mission criticaltargeting ultra-reliable low latency communications (URLLC) service.

A single component carrier bandwidth of 100 MHZ may be supported. In oneexample, NR resource blocks (RBs) may span 12 sub-carriers with asub-carrier bandwidth of 75 kHz over a 0.1 ms duration or a bandwidth of15 kHz over a 1 ms duration. Each radio frame may consist of 10 or 50subframes with a length of 10 ms. Each subframe may have a length of 0.2ms. Each subframe may indicate a link direction (i.e., DL or UL) fordata transmission and the link direction for each subframe may bedynamically switched. Each subframe may include DL/UL data as well asDL/UL control data. UL and DL subframes for NR may be as described inmore detail below with respect to FIGS. 9 and 10.

Beamforming may be supported and beam direction may be dynamicallyconfigured. MIMO transmissions with precoding may also be supported.MIMO configurations in the DL may support up to 8 transmit antennas withmulti-layer DL transmissions up to 8 streams and up to 2 streams per UE.Multi-layer transmissions with up to 2 streams per UE may be supported.Aggregation of multiple cells may be supported with up to 8 servingcells. Alternatively, NR may support a different air interface, otherthan an OFDM-based interface.

The NR RAN may include a central unit (CU) and distributed units (DUs).A NR BS (e.g., gNB, 5G Node B, Node B, transmission reception point(TRP), access point (AP)) may correspond to one or multiple BSs. NRcells can be configured as access cells (ACells) or data only cells(DCells). For example, the RAN (e.g., a central unit or distributedunit) can configure the cells. DCells may be cells used for carrieraggregation or dual connectivity and may not be used for initial access,cell selection/reselection, or handover. In some cases DCells may nottransmit synchronization signals (SS)—in some case cases DCells maytransmit SS. NR BSs may transmit downlink signals to UEs indicating thecell type. Based on the cell type indication, the UE may communicatewith the NR BS. For example, the UE may determine NR BSs to consider forcell selection, access, handover, and/or measurement based on theindicated cell type.

FIG. 7 illustrates an example logical architecture of a distributed RAN700, according to aspects of the present disclosure. A 5G access node706 may include an access node controller (ANC) 702. The ANC may be acentral unit (CU) of the distributed RAN 700. The backhaul interface tothe next generation core network (NG-CN) 704 may terminate at the ANC.The backhaul interface to neighboring next generation access nodes(NG-ANs) may terminate at the ANC. The ANC may include one or more TRPs708 (which may also be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs,or some other term). As described above, a TRP may be usedinterchangeably with “cell.”

The TRPs 708 may be a distributed unit (DU). The TRPs may be connectedto one ANC (ANC 702) or more than one ANC (not illustrated). Forexample, for RAN sharing, radio as a service (RaaS), and servicespecific AND deployments, the TRP may be connected to more than one ANC.A TRP may include one or more antenna ports. The TRPs may be configuredto individually (e.g., dynamic selection) or jointly (e.g., jointtransmission) serve traffic to a UE.

The local architecture 700 may be used to illustrate fronthauldefinition. The architecture may be defined that support fronthaulingsolutions across different deployment types. For example, thearchitecture may be based on transmit network capabilities (e.g.,bandwidth, latency, and/or jitter). The architecture may share featuresand/or components with LTE. According to aspects, the next generation AN(NG-AN) 710 may support dual connectivity with NR. The NG-AN may share acommon fronthaul for LTE and NR.

The architecture may enable cooperation between and among TRPs 708. Forexample, cooperation may be preset within a TRP and/or across TRPs viathe ANC 702. According to aspects, no inter-TRP interface may beneeded/present.

According to aspects, a dynamic configuration of split logical functionsmay be present within the architecture 700. The PDCP, RLC, MAC protocolmay be adaptably placed at the ANC or TRP.

FIG. 8 illustrates an example physical architecture of a distributed RAN800, according to aspects of the present disclosure. A centralized corenetwork unit (C-CU) 802 may host core network functions. The C-CU may becentrally deployed. C-CU functionality may be offloaded (e.g., toadvanced wireless services (AWS)), in an effort to handle peak capacity.A centralized RAN unit (C-RU) 804 may host one or more ANC functions.Optionally, the C-RU may host core network functions locally. The C-RUmay have distributed deployment. The C-RU may be closer to the networkedge. A distributed unit (DU) 706 may host one or more TRPs. The DU maybe located at edges of the network with radio frequency (RF)functionality.

FIG. 9 is a diagram 900 showing an example of a DL-centric subframe. TheDL-centric subframe may include a control portion 902. The controlportion 902 may exist in the initial or beginning portion of theDL-centric subframe. The control portion 902 may include variousscheduling information and/or control information corresponding tovarious portions of the DL-centric subframe. In some configurations, thecontrol portion 902 may be a physical DL control channel (PDCCH), asindicated in FIG. 9. The DL-centric subframe may also include a DL dataportion 904. The DL data portion 904 may sometimes be referred to as thepayload of the DL-centric subframe. The DL data portion 904 may includethe communication resources utilized to communicate DL data from thescheduling entity (e.g., UE or BS) to the subordinate entity (e.g., UE).In some configurations, the DL data portion 904 may be a physical DLshared channel (PDSCH).

The DL-centric subframe may also include a common UL portion 906. Thecommon UL portion 906 may sometimes be referred to as an UL burst, acommon UL burst, and/or various other suitable terms. The common ULportion 906 may include feedback information corresponding to variousother portions of the DL-centric subframe. For example, the common ULportion 906 may include feedback information corresponding to thecontrol portion 902. Non-limiting examples of feedback information mayinclude an ACK signal, a NACK signal, a HARQ indicator, and/or variousother suitable types of information. The common UL portion 906 mayinclude additional or alternative information, such as informationpertaining to random access channel (RACH) procedures, schedulingrequests (SRs), and various other suitable types of information. Asillustrated in FIG. 9, the end of the DL data portion 904 may beseparated in time from the beginning of the common UL portion 906. Thistime separation may sometimes be referred to as a gap, a guard period, aguard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the subordinate entity (e.g., UE)) to UL communication(e.g., transmission by the subordinate entity (e.g., UE)). One ofordinary skill in the art will understand that the foregoing is merelyone example of a DL-centric subframe and alternative structures havingsimilar features may exist without necessarily deviating from theaspects described herein.

FIG. 10 is a diagram 1000 showing an example of an UL-centric subframe.The UL-centric subframe may include a control portion 1002. The controlportion 1002 may exist in the initial or beginning portion of theUL-centric subframe. The control portion 1002 in FIG. 10 may be similarto the control portion 1002 described above with reference to FIG. 9.The UL-centric subframe may also include an UL data portion 1004. The ULdata portion 1004 may sometimes be referred to as the payload of theUL-centric subframe. The UL portion may refer to the communicationresources utilized to communicate UL data from the subordinate entity(e.g., UE) to the scheduling entity (e.g., UE or BS). In someconfigurations, the control portion 1002 may be a physical UL controlchannel (PUCCH).

As illustrated in FIG. 10, the end of the control portion 1002 may beseparated in time from the beginning of the UL data portion 1004. Thistime separation may sometimes be referred to as a gap, guard period,guard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the scheduling entity) to UL communication (e.g.,transmission by the scheduling entity). The UL-centric subframe may alsoinclude a common UL portion 1006. The common UL portion 1006 in FIG. 10may be similar to the common UL portion 1006 described above withreference to FIG. 10. The common UL portion 1006 may additional oralternative include information pertaining to channel quality indicator(CQI), sounding reference signals (SRSs), and various other suitabletypes of information. One of ordinary skill in the art will understandthat the foregoing is merely one example of an UL-centric subframe andalternative structures having similar features may exist withoutnecessarily deviating from the aspects described herein.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum)

Example HARQ LLR Buffer and Reordering Buffer Management

Hybrid automatic repeat request (HARQ) enables reliable communication byleveraging forward error-correcting coding at the physical layer andautomatic retransmissions at the data link/medium access layer based onACK/NACK (acknowledgment/negative acknowledgment) feedback on thereverse link. With HARQ, the receiver can store previously receivedpackets. The receiver can use the stored packets for joint processing(e.g., combining) with the last received packet (e.g., current packet)in order to enhance the decoding reliability. Examples of HARQmechanisms include Chase combining HARQ and Incremental Redundancy (IR)HARQ.

For HARQ Chase combining (also referred to as Chase-HARQ), thetransmitter (e.g., the encoder) repeats the same packet at eachretransmission. The receiver (e.g., the decoder) performs decoding(e.g., attempts to decode) a packet by combining all previously receivedpackets. For example, the decoder combines current receivedretransmitted packets with an original (e.g., previously received andstored) erroneously transmitted packet from a previous transmission,where the retransmissions are identical copies of the originaltransmission. This may involve all previously received packets of thecurrent combined packet obtained from all previous transmissions.

For HARQ IR combining (also referred to as IR-HARQ), at eachretransmission, the transmitter sends a packet consisting of new paritybits. The receiver stores all the previously received packets. Forexample, additional redundant information is transmitted in eachretransmission to increase a channel coding gain, where theretransmissions consist of new parity bits from the channel encoder.Different bits (e.g., new parity bits) can be transmitted by employing adifferent rate matching (puncturing) pattern, for example, which resultsin a smaller effective code rate of the stream.

FIG. 11 is a representation 1100 of a HARQ LLR circular buffer based ona turbo code and rate matching scheme. As shown in FIG. 11, systematicbits and redundant bits can be interleaved. Systematic bits are theoriginal input data bits, while parity bits (e.g., parity packets) areused to find/correct errors that may occur during data transmission.With Chase combining, the same RV index is sent. IR-HARQ may be based ona redundancy version (RV) sequence 0, 2, 3, 1 and Chase/ARQ may be basedon RV sequence 0, 0, 0, 0 (no LLR combining for ARQ). Note that, theproposed scheme works with other channel coding schemes as well, such asLDPC, convolutional and polar codes.

One challenge to implementing HARQ is storage of data from previouslyreceived packets in a HARQ buffer at the receiver. Buffered packets atthe receiver can be represented by quantizing log likelihood ratios(LLRs) of the coded bits. The LLR is a soft decision that indicates thelikelihood of the coded bit being a 1 or 0. In certain systems (e.g.,long term evolution (LTE) systems), LLRs for an entire round trip time(RTT) duration (e.g., 8-10 ms for LTE) may be buffered (e.g., stored ina buffer). The LLRs may be buffered, for example, in the physical layer(PHY) HARQ LLR buffer. In addition, for radio link control (RLC) ARQ,data may also be stored, for example, in the higher layer reorderingbuffer. For example, data may be stored for up to two back-to-back HARQprocesses of up to four retransmissions each (e.g., 60-100 ms worth ofdata for LTE).

The difficulty increases as transmission rates increase and largerbandwidth is used. The buffer size may be based on the data throughput,buffer duration, number of interlaces, and LLR bitwidth. Scaling up theLTE HARQ/ARQ design can incur large buffer cost. Certain systems maysupport higher throughput rates (e.g., NR systems including 5G systems).In one example, if the throughput is scaled by a factor of ten (10 Gbpsas compared to 1 Gbps), the overhead may be increased also by a factorof ten for the same buffer duration, number of interlaces, and LLRbitwidth.

Accordingly, techniques and apparatus for buffer management aredesirable, for example, to reduce overhead buffer size cost for systemssupporting high throughput.

Certain aspects of the present disclosure discuss techniques for HARQbuffer and reordering buffer management, including low-bitwidth LLRquantization design and a shared HARQ LLR and RLC (ARQ) reorderingbuffer.

Example Low-Bitwidth LLR Quantization Design

FIG. 12 illustrates example operations 1200 that may be performed by areceiver (e.g., decoder), such as a wireless node (e.g., UE 206 or BS204), for reducing overhead buffer size, in accordance with certainaspects of the present disclosure.

Operations 1200 begin, at 1202, by receiving one or more packets of atleast one of an initial transmission or a retransmission. At 1204, thewireless node forms one or more log likelihood ratios (LLRs) based onthe one or more packets. At 1206, the wireless node compresses the oneor more LLRs by quantizing the one or more LLRs. At 1208, the wirelessnode buffers the one or more compressed LLRs. Examples of LLR softbuffer management include IR-HARQ with heavy non-uniform multi-levelquantization (e.g., 3-level quantization or 2-level (1-bit)quantization). This can result in a net coding gain (E_(b)/N₀ gain) ofIR-HARQ offsets and/or low precision LLR buffering over Chase combining.

According to certain aspects, a low-bitwidth LLR quantization design canbe used. In one example implementation, LLRs can be quantized tomultiple levels, such as 3-levels (e.g., for three possibilities such as−LLR, 0, LLR or represented as 0, 1, 2). This provides performance gainover binary 1-bit LLR quantization. FIG. 13 is a block diagramillustrating 3-level LLRs compressed into binary format, in accordancewith certain aspects of the present disclosure. For example, as shown inFIG. 13, groups of five LLRs (LLR1-LLR5) can be input to the quantizer1302 and quantized to 3-levels (multi-level LLR1-LLR5 output). In thiscase, there are 3⁵=243 possible combinations for the 5 LLRs each having3 possibilities. Converting this to a binary format, the 243 possiblecombinations are <256 combinations and, therefore, can be mapped to8-bits using a look up table (LUT) 1304 to output the quantized LLRvector. Thus, every 5 LLRs may be quantized to 3 levels and mapped to 8bits. Each LLR may be represented by 8/5=1.6 bits per LLR. Thus, 1.6bits can be used to store each LLR. This may be roughly half the numberof bits used to store 3-bit LLRs. Compared with Chase combining, thisrepresents significant performance gain.

In another example implementation, groups of 2 LLRs can be compressed.For example, one LLR can be quantized to 3-levels and another LLR can bequantized to 5-levels. Thus, the number of combinations for LLRs is3×5=15 (a 4-bit value). In this case, the LLRs can be compressed into a4-bit storage unit. Alternatively, one LLR can be quantized to 2-levelsand compressed to 1-bit.

Thus, HARQ IR with quantized LLRs may have gain over Chase combining.The graph 1400 in FIG. 14 illustrates an example of the performance gapbetween Chase combining and IR HARQ. Graph 1400 shows an Eb/N0 versuscapacity curve representing efficiency of various coding schemes. Curve1402 represents the Additive White Gaussian Noise channel (AWGN)capacity curve. Curve 1404 represents the Binary Phase Shift Keying(BPSK) Capacity curve. Curve 1406 represents the BPSK capacity curvewith 1-bit LLR quantization after the second transmission (that is thefirst two transmission LLRs are quantized and the third transmission LLRis still in full precision).

As shown in FIG. 14, Eb/N0 gain by going to a lower coding rate mayoffset the loss due to heavy LLR quantization. An even larger gap may beexpected over fading channels due to high rate capacity saturation. Fora high reliability 5G HARQ design, a high coding rate (e.g., modulationand coding scheme (MCS)) can use IR HARQ to achieve Eb/N0 gain.Aggressive LLR quantization can be used to manage buffer size. Netcoding gain (e.g., Eb/N0 gain) of IR HARQ with heavy quantization may beused to offset low precision LLR buffering over Chase-HARQ. Low codingChase-HARQ combining may incurs limited Eb/N0 loss and at the same timeprovides reasonable performance compared with IR HARQ.

According to certain aspects, the UE can signal to the BS (e.g., a gNB)it's capability to compress the LLR buffer (i.e., perform LLRquantization and compression). This may allow higher throughput to beachieved for a given soft buffer constraint. The UE may signal itspreferred lowest code rate after HARQ transmissions along with themaximum soft buffer size. Thus, the BS may be able to distinguish (e.g.,determine) the lowest code rate to support at different throughoutlevels.

Example Shared HARQ LLR and Reordering Buffer

According to certain aspects, a joint HARQ LLR and ARQ reordering buffer(e.g., across the medium access control (MAC), radio link control (RLC),and packet data convergence protocol (PDCP) protocol layers) can beused. FIG. 15 illustrates example operations 1500 that may be performedby a receiver, such as a wireless node (e.g., UE 206 or BS 204), forreducing overhead buffer size, in accordance with certain aspects of thepresent disclosure.

Operations 1500 begin, at 1502, by receiving an initial transmission ora retransmission comprising one or more transmission blocks on at leastone of multiple component carriers (CCs) or multiple hybrid automaticrepeat request (HARQ) interlaces. At 1504, the wireless node attempts todecode the one or more transmission blocks. At 1506, the wireless nodedetermines whether the one or more transmission blocks were successfullydecoded. At 1508, the wireless node stores soft log likelihood ratios(LLRs) associated with transmission blocks that failed to successfullydecode in a shared buffer. At 1510, the wireless node storestransmission blocks that were successfully decoded out-of-order in theshared buffer.

According to certain aspects, the UE may signal, to the BS (e.g., agNB), it's capability to manage a joint LLR and RLC buffer (e.g.,capability to store the LLRs and transmission blocks that weresuccessfully decoded out-of-order in the shared buffer). Thus, the BSmay know (e.g., determine) that the UE qualifies as a higher UE categoryand may be capable of achieving higher throughput for a given soft LLRbuffer and RLC buffer constraint.

FIG. 16 illustrates a PHY HARQ interlace on single CC and FIG. 17illustrates a PHY HARQ interlace on multiple CCs. Although a single PHYHARQ interlace is shown, there could also be multiple PHY HARQinterlaces. The out-of-order delivery issue may still exist formulti-interlace or carrier aggregation (CA) cases. As shown in FIG. 17,a transport block (TB) may be HARQ retransmitted until it passes (e.g.,is successfully received/decoded, which may be until an ACK is receivedby the transmitter) or until the HARQ retransmissions fails a certainnumber of times (e.g., after a threshold number of retries or expiry ofa timer). LLRs corresponding to failed transmissions and/orretransmissions may be stored (e.g., in the HARQ LLR buffer). Afterfailing PHY HARQ retransmission, the TB may be sent to the RLC layer forretransmission until the TB passes. In some cases, the RLCretransmissions may also fail. In the example shown in FIG. 17, oncertain CCs (and/or HARQ interlaces), the transmissions andretransmissions keep failing (e.g., on CC1 and CC2), while transmissionson other CCs (and/or HARQ interlaces) pass (e.g., CC0 and CC3). This maylead to out of order packet delivery. Thus, a reordering buffer (e.g.,the ARQ reordering buffer) may be used to store packets so that they canbe reordered and delivered in order to an upper layer.

According to certain aspects, a joint (e.g., shared) HARQ LLR and RLCreordering buffer may be used to reduce overall storage overhead forHARQ operations. The HARQ LLR buffer and reordering buffer storecomplementary information (e.g., the HARQ LLR buffer stores failed TBsand the ARQ reordering buffer stores out of order passing TBs after a TBfailure event). The shared buffer may be jointly managed at the receiverside, for example, using a same memory as dynamic partitioning memory.

According to certain aspects, for RLC retransmissions, RLCretransmissions may be sent on certain CCs (and/or HARQ interlaces) andRLC parity packets (e.g., RLC PDUs) may be sent on other CCs (and/orHARQ interlaces), as shown in FIG. 18. For example, as shown in FIG. 18,RLC retransmissions are sent on CC1 and CC2, on which transmissions andretransmission keep failing, and RLC parity packets are sent on CC0 andCC3, on which transmissions and keep passing. In this case, even if theRLC retransmissions fail (e.g., on CC1 and/or CC2), some or all of theRLC parity packets (e.g., on CC0 and/or CC3) may still be successfullydecoded. The successfully decoded parity packets, along with othersystematic data packets, may be used to decode the lost data packets(e.g., the failed retransmissions on the other CCs). After decoding thelost data packets, the receiver may be able to send an ACK and theretransmissions can be halted.

Thus, transmission of RLC parity packets (e.g., redundant packets overmultiple CCs and/or HARQ interlaces) may be used to improve reliabilityof data packets (e.g., due to coding gain). Further, bycontrolling/adjusting the amount (e.g., the number of) transmitted RLCparity packets, data transmission can be tapered down (e.g., throttledown transmission of new data throughput), for example, to limit thebuffer size requirement.

On the transmitter side, a timer (e.g., a HARQ timer) can be associatedwith the data rate. The timer may limit the duration for attemptingretransmissions of a failed TB. In aspects, for lower data rates alonger timer may be used because a smaller amount of information isbeing buffered, while for higher data rates a shorter timer may be usedsince a larger amount of information is being buffered.

FIG. 19 illustrates example operations 1900 that may be performed by atransmitter, such as a wireless node (e.g., a UE 206 or BS 204), inaccordance with certain aspects of the present disclosure.

Operations 1900 begin, at 1902, by sending a retransmission on at leastone of multiple CCs or HARQ interlaces. At 1904, the wireless node sendsone or more parity packets associated with at least a portion of theretransmission. At 1906, retransmission is halted if an acknowledgment(ACK) is received. For example, an ACK may be received when a sufficientnumber of parity packets are successfully decoded in order to recoverlost data packets.

Joint HARQ/ARQ buffer management may improve memory utilizationefficiency. For example, when the reordering buffer watermark is low,high LLR bitwidth can be used for improved performance; and when thereordering buffer watermark is high, low LLR bitwidth can be applied inthe HARQ buffer and RLC ARQ parity packets can be used on top ofretransmissions to tradeoff overhead for low latency/high reliability.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

In some cases, rather than actually transmitting a frame, a device mayhave an interface to output a frame for transmission. For example, aprocessor may output a frame, via a bus interface, to an RF front endfor transmission. Similarly, rather than actually receiving a frame, adevice may have an interface to obtain a frame received from anotherdevice. For example, a processor may obtain (or receive) a frame, via abus interface, from an RF front end for transmission.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering.

For example, means for determining, means for forming, means forcompressing, means for receiving, means for buffering, means forstoring, means for compressing, means for halting, means for quantizing,means for attempting, means for sending, and/or means for adjusting maycomprise a processing system, which may include one or more processors,such as the TX processor 616, transmitter(s) 618, and/or thecontroller/processor 675 of the wireless base station 610 illustrated inFIG. 6, and/or the TX processor 668, the transmitter(s) 654, and/or thecontroller/processor 659 of the user equipment 650 illustrated in FIG.6. Means for transmitting and/or means for sending may comprise atransmitter, which may include TX processor 616, transmitter(s) 618,and/or the antenna(s) 620 of the wireless base station 610 illustratedin FIG. 6, and/or the TX processor 668, the transmitter(s) 654, and/orthe antenna(s) 652 of the user equipment 650 illustrated in FIG. 6.Means for receiving may comprise a receiver, which may include RXprocessor 670, receiver(s) 618, and/or the antenna(s) 620 of thewireless base station 610 illustrated in FIG. 6, and/or the RX processor656, the receiver(s) 654, and/or the antenna(s) 652 of the userequipment 650 illustrated in FIG. 6.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a wirelessnode (see FIG. 1), a user interface (e.g., keypad, display, mouse,joystick, etc.) may also be connected to the bus. The bus may also linkvarious other circuits such as timing sources, peripherals, voltageregulators, power management circuits, and the like, which are wellknown in the art, and therefore, will not be described any further. Theprocessor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer-readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, ROM (ReadOnly Memory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a wireless node and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a wirelessnode and/or base station can obtain the various methods upon coupling orproviding the storage means to the device. Moreover, any other suitabletechnique for providing the methods and techniques described herein to adevice can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method to reduce buffer overhead, comprising:receiving packets comprising an initial transmission and at least oneincremental redundancy hybrid automatic repeat request (IR-HARQ)retransmission; forming a plurality of log likelihood ratios (LLRs)based on the packets; compressing the plurality of LLRs, including:quantizing groups of five LLRs to three levels each; and mapping eachgroup of five quantized three-level LLRs to eight bits using a lookuptable (LUT); and buffering the compressed plurality of LLRs.
 2. Themethod of claim 1, wherein the compressing the plurality of LLRscomprises: quantizing the plurality of LLRs to a non-uniformmultiple-level quantization.
 3. A method to reduce buffer overhead,comprising: receiving packets comprising an initial transmission and atleast one incremental redundancy hybrid automatic repeat request(IR-HARQ) retransmission; forming a plurality of log likelihood ratios(LLRs) based on the packets; compressing the plurality of LLRs,including: quantizing a first LLR to three levels; quantizing a secondLLR to five levels; and mapping the first quantized three-level LLR andthe second quantized five-level LLR to four bits using a lookup table(LUT); and buffering the compressed plurality of LLRs.
 4. The method ofclaim 1, further comprising combining the buffered compressed pluralityof LLRs using IR combining.
 5. The method of claim 1, wherein thebuffered compressed plurality of LLRs comprise systematic bits andredundancy bits.
 6. The method of claim 1, wherein: receiving thepackets comprises receiving the packets at a receive processor of a userequipment (UE), buffering the compressed LLRs comprises storing thecompressed LLRs in one or more buffers of the UE, and the method furthercomprises signaling, to a base station (BS), a capability of the UE toperform the LLR compression.
 7. The method of claim 1, furthercomprising: signaling, to a base station (BS), a preferred minimum coderate, after HARQ transmissions, and a maximum soft buffer size.
 8. Amethod to reduce buffer overhead, comprising: receiving a radio linkcontrol (RLC) retransmission comprising one or more transmission blockson at least one of multiple component carriers (CCs) or multiple hybridautomatic repeat request (HARQ) interlaces; receiving at least one RLCparity packet associated with the RLC retransmission on at least one ofa different CC or a different HARQ interlace than the RLCretransmission; attempting to decode the one or more transmissionblocks; determining whether the one or more transmission blocks weresuccessfully decoded; storing soft log likelihood ratios (LLRs)associated with transmission blocks that failed to successfully decodein a shared buffer; and storing transmission blocks that weresuccessfully decoded out-of-order in the shared buffer.
 9. The method ofclaim 8, wherein the shared buffer comprises a joint HARQ LLR and radiolink control (RLC) reordering buffer.
 10. The method of claim 8, whereinthe shared buffer comprises dynamic partitioning memory.
 11. The methodof claim 8, further comprising: signaling, to a base station (BS), acapability to store LLRs and transmission blocks that were successfullydecoded out-of-order in the shared buffer.
 12. An apparatus havingreduced buffer overhead, comprising: means for receiving packetscomprising an initial transmission and at least one incrementalredundancy hybrid automatic repeat request (IR-HARQ) retransmission;means for forming a plurality of log likelihood ratios (LLRs) based onthe packets; means for compressing the plurality of LLRs, including:quantizing groups of five LLRs to three levels each; and mapping eachgroup of five quantized three-level LLRs to eight bits using a lookuptable (LUT); and means for buffering the compressed plurality of LLRs.13. The apparatus of claim 12, wherein the means for compressing theplurality of LLRs comprises: means for quantizing the plurality of LLRsto a non-uniform multiple-level quantization.
 14. An apparatus havingreduced buffer overhead, comprising: means for receiving packetscomprising an initial transmission and at least one incrementalredundancy hybrid automatic repeat request (IR-HARQ) retransmission;means for forming a plurality of log likelihood ratios (LLRs) based onthe packets; means for compressing the plurality of LLRs, including:quantizing a first LLR to three levels; quantizing a second LLR to fivelevels; and mapping the first quantized three-level LLR and the secondquantized five-level LLR to four bits using a lookup table (LUT); andmeans for buffering the compressed plurality of LLRs.
 15. The apparatusof claim 12, further comprising means for combining the bufferedcompressed plurality of LLRs using IR combining.
 16. The apparatus ofclaim 12, wherein the buffered compressed plurality of LLRs comprisesystematic bits and redundancy bits.
 17. An apparatus having reducedbuffer overhead, comprising: means for receiving a radio link control(RLC) retransmission comprising one or more transmission blocks on atleast one of multiple component carriers (CCs) or multiple hybridautomatic repeat request (HARQ) interlaces; means for receiving at leastone RLC parity packet associated with the RLC retransmission on at leastone of a different CC or a different HARQ interlace than the RLCretransmission; means for attempting to decode the one or moretransmission blocks; means for determining whether the one or moretransmission blocks were successfully decoded; means for storing softlog likelihood ratios (LLRs) associated with transmission blocks thatfailed to successfully decode in a shared buffer; and means for storingtransmission blocks that were successfully decoded out-of-order in theshared buffer.
 18. The apparatus of claim 17, wherein the shared buffercomprises a joint HARQ LLR and radio link control (RLC) reorderingbuffer.
 19. The apparatus of claim 17, wherein the shared buffercomprises dynamic partitioning memory.